welcome.
I’d call that “texture analysis”.
you could run a grayscale dilation and erosion of a given kernel and radius, then take the difference of those, and that will be the range of values for a local neighborhood.
this doesn’t cope with salt-and-pepper noise too well.
or you could run a sobel/laplacian, abs/square the values, then grayscale dilate (to find local maximum).
edit: I’d even suggest simply looking at the erosion, not taking difference between dilation and erosion… in this situation. the data is such that you get a better signal from just the erosion.